1. Field of the Invention
The invention relates to antenna technology generally and, more particularly, to directive phased arrays.
2. Description of the Prior Art
In the prior art, slotted waveguide antennas have been used and extensively described in the technical and patent literature. In the text, "Radar Handbook" by Merrill I. Skolnik (McGraw Hill 1970), for example, a planar array formed of a plurality of slotted waveguide linear subarrays is shown and discussed in Chapter 13, dealing with frequency-scanned arrays. U.S. Pat. No. 3,740,751 discloses a slotted-waveguide array with dual slots for improved bandwidth and greater scanning angle capability. Other references are also available, and accordingly, the performance of such arrays is relatively well known.
The meander line antenna is also known per se. Where such a line, drawing basically from microwave stripline technology, is placed between conductive planes, it is sometimes referred to as a "Sandwich Wire Antenna." In 1957, such an antenna was described by W. Rotman and N. Karas in "The Sandwich Wire Antenna: a New Type of Microwave Line Source Radiator," appearing in the IRE Nat. Conference Record 1957, Pt. 1, pp 162-172. Those authors further described such devices in an article entitled "The Sandwich Wire Antenna," (Microwave Journal, Vol. 2, August 1959. A still more recent reference appeared in the IEEE Trans. Antenna and Propogation, Vol. AP-19 No. 5, September 1971, under the title "A New Analysis of the Sandwich Wire Antenna."
In operating arrays adjacently at different frequencies there are a number of interference and blockage problems which can be identified. These are particularly evident on shipboard where more than one view of the environment is desirable. The problems are particularly significant where target tracking (for example) is to be handed over from a system operating at a second frequency,. Prior art arrangements of the type have also suffered from the displacement of antenna phase centers from one array to another.
The manner in which the invention improves upon the prior art to provide integration of essentially two scannable arrays operating in different frequency bands into one overall antenna aperture will be evident as this description proceeds.